Windows Activation Prompt Issue

Wanted to see if anyone else has come across this and if they found a solution. I have a build that is a system image that has been syspreped. When the build gets to the post install task the windows activation screen comes up. After a couple of minutes it closes and then starts the post install task. The very first post install task is to add the key and the build finishes fine. I'd like to not see the activation screen as it slows the build done. Any help would be great.